Section numbering with numbering like 1.11

Question

How do I set my section numbers like the given format? I'm in need of the format given below.

I'm using gsm-l.cls. I'm just using tags like:

\chapter{name}
\section{sectionname}
\begin{theorem}
\end{theorem}

Example:

Chapter 1
1.1. Section name
Theorem: 1.1.1.
Theorem: 1.1.2.
Remark: 1.1.3.

Answer 1

Here's how you can do it:

\documentclass{gsm-l}

% section numbers preceded by chapter number
\renewcommand{\thesection}{\thechapter.\arabic{section}}

% define the theorem environments
\newtheorem{theorem}{Theorem}[section] % theorems are numbered by section

\theoremstyle{remark}
\newtheorem{remark}[theorem]{Remark} % remarks share the theorem counter

\begin{document}
\chapter{Chapter title}
\section{Section title}
\begin{theorem}
$1+1=2$
\end{theorem}
\begin{remark}
The above theorem is hard.
\end{remark}
\end{document}

Answer 2

the usual recommendation for ams document classes (of which gsm-l.cls is one) is to include the command

\numberwithin{section}{chapter}

in the preamble.